Luke 9:62 (KJV) And Jesus said unto him, No man, having put his hand to the plow, and looking back, is fit for the kingdom of God.
Genesis 19:17-26 (KJV)
And it came to pass, when they had brought them forth outside, that he said, Escape for your life; look not behind you, neither stay in all the plain; escape to the mountain, lest you be consumed.
... Then the LORD rained upon Sodom and upon Gomorrah brimstone and fire from the LORD out of heaven;
And he overthrew those cities, and all the plain, and all the inhabitants of the cities, and that which grew upon the ground.
But his wife looked back from behind him, and she became a pillar of salt.